tmpdir: port to VMS, to // != /, and to long dirs

* lib/tmpdir.c (__libc_secure_getenv) [!_LIBC]: Rename from
__secure_getenv, so that we're more like the glibc version.
All uses changed.
(path_search): Don't put slash after directory if __VMS.
Problem reported by Steven M. Schweda in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-07/msg00019.html>.
Do not remove trailing slash from "//".
Do not assume dlen <= INT_MAX.
* lib/tmpdir.c: Simplify code to add slash; no need for a loop.
tmpdir: fix typo in previous change
tmpdir: fix bug in VMS port

* lib/tmpdir.c (path_search) [__VMS]: Never add slash.
See Steven M. Schweda in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-07/msg00026.html>.
bootstrap: use correct source when copying build-aux files

in my setup for ttfautohint (http://repo.or.cz/w/ttfautohint.git) I
have the following assignment in `bootstrap.conf':

  build_aux=gnulib

It seems that the patch below is necessary to make this really work
(at least it works for me): if I understand the issue correctly,
$build_aux is a *destination* variable, so it must not be used for the
files listed in $gnulib_extra_files which uses the directory structure
of the `gnulib' repository.

* build-aux/bootstrap (gnulib_extra_files): This variable is
relative to upstream gnulib layout, not downstream.

Signed-off-by: Eric Blake <eblake@redhat.com>
autoupdate
gettext: update to version 0.18.3

* m4/intl.m4, m4/po.m4: Update from gettext-0.18.3.  In particular,
require AC_PROG_SED to allow user to specify custom sed command when
generating en@quot PO file.
localecharset: make locale_charset thread-safe on Mac OS X

* lib/localcharset.c (locale_charset) [DARWIN7]: Use MB_CUR_MAX_L
instead of MB_CUR_MAX.
autoupdate